I feel like you dont understand something here.
but all sound speeds are same no matter their frequency.

So rockets are coming down at super sonic speed as in faster than sound so you cant hear them.
When they start breaking and speed goes below sonic and that wave front that bunch up together is so called sonic boom. if you dont hear 2 kinda booms. must be something wrong with your sound since you want to see them.
But you probably want to talk about that circle thing that happens when sonic barrier is broken around the plane.
Im not sure how this works in reverse since this was not breaking the speed barrier but going under.

#4 #8 #9 Technically they didn’t make “two” big bangs, they each made three bangs, because each booster assembly breaks the sound barrier when it’s coming back to earth in triplicate. You can hear it as a “boom-ba-BOOM” a little ways after you can see the boosters themselves re-ignite for landing. The roar you hear immediately after the sonic booms is from the rocket engines themselves.
“The first boom is from the aft end (engines),” said John Taylor, SpaceX’s Communications Director. “The second boom is from the landing legs at the widest point going up the side of the rocket. The third boom is from the fins near the forward end.”

#11 well according to my video each boom has 2 booms so close to each other that we think it is one.
Now they say each rocket has its own 3 booms.
3 booms per rocket times 2 rockets times 2 booms per one is 12.
Im surprised we hear anything at all.

#11 ????? Each booster makes three quick booms (boom-ba-BOOM) . Two times three is just six total
even though if you were not aware of what to listen for it just sounds like a boom from one booster
followed a boom from the second booster.